RS232 to RS485 conversion, RTS as control line.

Started by Ajab in comp.arch.embedded12 years ago 3 replies

Hi people, I am using a MAX3221 IC to convert RS232 to TTL and MAX3465 full duplex IC to convert TTL to RS485. Shorted TX+, RX+ and TX-, RX-...

Hi people, I am using a MAX3221 IC to convert RS232 to TTL and MAX3465 full duplex IC to convert TTL to RS485. Shorted TX+, RX+ and TX-, RX- for 2- wire RS485 protocol. RTS line is used for controlling enable of max3465. DE and ~RE are given to TTL RTS. But the RTS always remains high.. so for max3465 driver will be always enabled....... So how the receiver portion will work, because RTS...


RS485 half duplex and full duplex questions

Started by Anonymous in comp.arch.embedded12 years ago 3 replies

regards: by the way could I ask a question,could I simply use the "RTS line" to control RS485 half duplex mode? and I ask a question. and...

regards: by the way could I ask a question,could I simply use the "RTS line" to control RS485 half duplex mode? and I ask a question. and when I am using RS485 FULL duplex (RS422 mode),Do I need any control lines like "RTS","CTS"? any positive suggestion is welcome. best regards to you all mike


Cheap Processors with Fast USARTs for RS485?

Started by Christopher Graham in comp.arch.embedded15 years ago 5 replies

I want to implement low cost rs485-connected data collection nodes, and need to choose a microcontroller for them that will support baud rates...

I want to implement low cost rs485-connected data collection nodes, and need to choose a microcontroller for them that will support baud rates of more than say 400 kbps, preferably up to 1 mbps. I know there are some PIC18Fxxxx's that have an "Advanced UART" that are claimed do this. Other alternatives? - Chris


Ask RS485 Trouble ?

Started by TR6 in comp.arch.embedded13 years ago 4 replies

Hi, I have built RS485 communication for 11 AT89S51 microcontrollers. Consist 1 master and 10 slave nodes. I use SN75176BP for RS485 driver....

Hi, I have built RS485 communication for 11 AT89S51 microcontrollers. Consist 1 master and 10 slave nodes. I use SN75176BP for RS485 driver. All microcontrollers connected using UTP Cat-5 Cables in a bus : Safe bias resistor-SL1-SL2-SL3-SL4-SL5-SL6-MA-SL7-SL8-SL9-SL10-resistor terminator. From SL1 to SL7 connection works fine, but from SL8 to SL10 still cannot connected. Total length of cables ...


rs485 question

Started by JY Kim in comp.arch.embedded12 years ago 4 replies

Hello. I am software enginer and working with board with rs485 rs485 transceiver is 3.3V ST3485E and is connected with PLC. When I send data...

Hello. I am software enginer and working with board with rs485 rs485 transceiver is 3.3V ST3485E and is connected with PLC. When I send data from my board to PLC, voltage level is 3.3V but PLC send 5V data. PLC recognize 3.3V input data in 1200bps but not 9600 bps. when PLC recognize 1200bps signal it sends reponse which my board can recognize. and garbage data that PLC doesn't send is c...


How to test RS485 in loopback?

Started by kaczfan in comp.arch.embedded13 years ago 4 replies

Hi. When I want to test RS232, I simply cross Tx and Rx pins (2 and 3 in DB9). In RS485, on the other hand, there are four pins used for...

Hi. When I want to test RS232, I simply cross Tx and Rx pins (2 and 3 in DB9). In RS485, on the other hand, there are four pins used for transmission, ie Tx+, Tx-, Rx+, Rx-. Is it enough to connect Rx+ to Tx+ and Rx- to Tx-, or is there any connection that should also be done? What are the possible reasons for the lack of transmission?


RS485 CSMA/CD protocol

Started by therion in comp.arch.embedded14 years ago 35 replies

Hi, I would need to implement an CSMA/CD L1 protocol code for RS485 in my new AVR project for home automation. Any link, hint or help for the...

Hi, I would need to implement an CSMA/CD L1 protocol code for RS485 in my new AVR project for home automation. Any link, hint or help for the similar source code?


off the shelf RS485 network card

Started by Shane williams in comp.arch.embedded9 years ago 15 replies

We have systems where a bunch of microcontrollers (up to 250) need to communicate with each other in a circular ring. All controllers need to...

We have systems where a bunch of microcontrollers (up to 250) need to communicate with each other in a circular ring. All controllers need to see all messages and if there is a single break in the ring, it needs to continue working and report the fault. It doesn't need to be high speed, 200 kbps would probably do. Are there any RS485 network cards that can do this and how much do they cost...


RS485 with +-15V common mode

Started by Ralph Malph in comp.arch.embedded16 years ago 10 replies

Boy, I thought it was tough finding an I2C port expander chip that fit all my requirements. I am looking for an RS485 tranceiver that I can use...

Boy, I thought it was tough finding an I2C port expander chip that fit all my requirements. I am looking for an RS485 tranceiver that I can use along with an RS232 chip to allow either protocol through the same pins. But I can't find an acceptable chip anywhere. This was discussed a few weeks ago, but I don't think anyone mentioned any part numbers that were compatible. I think I can f...


Lightening protection ?

Started by Alex Gibson in comp.arch.embedded12 years ago 6 replies

Can someone suggest the most reliable way for lightening protecting a three wire rs485 setup. Boards on the structure(steel) will be...

Can someone suggest the most reliable way for lightening protecting a three wire rs485 setup. Boards on the structure(steel) will be connected via 6 or 8 core twisted shielded. Three wires for rs485,then +24VDC , pwr gnd and a few spare. Option for separate power cable if required. I was planning on using transorbs or similar to protect all the lines at each board location with the...


RS485: testing loopback

Started by Ajab in comp.arch.embedded12 years ago 1 reply

I am using a rs232 to wire rs485 converter. I have shorted TX+ with RX + and TX- with RX- for 2-wire configuuration. A 120R termination resistor...

I am using a rs232 to wire rs485 converter. I have shorted TX+ with RX + and TX- with RX- for 2-wire configuuration. A 120R termination resistor is connected between TX+ and TX-. I am using it in half-duplex configuration. Is it possible to test loopback. Because in half-duplex either tx or rx will be enabled. I have not tried this. Just before trying want to check if this will work.


RS485 with SN75176 - TX collision

Started by djordj in comp.arch.embedded9 years ago 12 replies

Hi, coming back after the RS485 bus has been setup. Going on investigating about possible problems, we've found that we're defenseless against...

Hi, coming back after the RS485 bus has been setup. Going on investigating about possible problems, we've found that we're defenseless against transmitters collisions: if a slave get stuck in transmitter mode (DE=1 in SN75176) when the master take the bus control, we have a fault on the line. So I made up a test board with two transceivers: the first one fixed on transmission mode (DE[1]=1...


bombproof RS485 chips?

Started by Dennis Clark in comp.arch.embedded15 years ago 12 replies

Hi all, I'm working a project where I've got several RS485 nodes cabled together in about as hostile environment as I can imagine. High...

Hi all, I'm working a project where I've got several RS485 nodes cabled together in about as hostile environment as I can imagine. High powered vacuum pumps, high current stepper motors, high static discharge possibilities, etc. Can anyone suggest an 8 pin part that is REALLY bombproof to static and CMI? I know that the TI 75176B is right out, but who is in? thanks, DLC -- =====...


Different devices on RS485 line?

Started by ElderUberGeek in comp.arch.embedded12 years ago 2 replies

As RS485 is multi-drop, one would assume that you can hang multiple devices on the same line (meaning different devices of different makes,...

As RS485 is multi-drop, one would assume that you can hang multiple devices on the same line (meaning different devices of different makes, like say two controllers from two different manufacturers). I have two questions: 1. Is this at all possible, or should all devices on the 485 line be the same type/make 2. If possible, what should I check about the 485 parameters/protocols to ensure ...


RS485 bus and auto-addressing

Started by pozz in comp.arch.embedded6 years ago 49 replies

I have a small RS485 two-wires network with about ten nodes. I have a master that initiates the communication on the bus. All the other nodes...

I have a small RS485 two-wires network with about ten nodes. I have a master that initiates the communication on the bus. All the other nodes are always in receiving state and start transmitting only if the message from the master is addressed to them. A simple method to assign an address to a slave is to have a set of jumpers/dip-switch on the board, but during the installation/setup ...


RS485 half duplex and full duplex question

Started by Anonymous in comp.arch.embedded12 years ago 5 replies

regards: How could I test RS485(half duplex) or RS422(full duplex) any positive suggestion is welcome. best regards to you...

regards: How could I test RS485(half duplex) or RS422(full duplex) any positive suggestion is welcome. best regards to you all mike-smith


RS485 over optical fiber cable

Started by pozz in comp.arch.embedded10 months ago 32 replies

I'd like to replace an electrical cable with a fiber cable, mainly for electromagnetic noise immunity and long distance (I need to reach...

I'd like to replace an electrical cable with a fiber cable, mainly for electromagnetic noise immunity and long distance (I need to reach 500m). The bitrate will be very low: 9600bps is ok. I need to keep the cost low as possible. I never used fiber cables before. In similar applications I used RS485 transceivers connected to the UART peripheral of an MCU. I think I need a fiber optic c...


Looking for 9 bit RS485 solutions

Started by Anonymous in comp.arch.embedded12 years ago 12 replies

Hi, We have various products that interface to Point Of Sale terminals (a.k.a. cash registers). These use IBM's 4683 protocol which is a...

Hi, We have various products that interface to Point Of Sale terminals (a.k.a. cash registers). These use IBM's 4683 protocol which is a 9 bit (address bit) RS485 bus. We'd like to build some test tools so we don't have to always use a POS terminal. Anyone know of any 9bit 485 adapters, converters, etc.? My strong preference is a USB/Ethernet to 9 bit 485 adapter. Second preference ...


OT: Ethernet extender

Started by Robert Anderson in comp.arch.embedded10 years ago 5 replies

A bit OT for the group, but it is related to an embedded system ... I have an application that requires Ethernet to be extended through an...

A bit OT for the group, but it is related to an embedded system ... I have an application that requires Ethernet to be extended through an existing RS485 serial link, such that I have Ethernet RS485 Ethernet. I'm aware that there are any number of copper wire Ethernet extenders that will work on bare copper, but unfortunately I have the serial link in the path so I can't get to t


8051 serial problems

Started by Edo Reshef in comp.arch.embedded15 years ago 15 replies

Hi, I have an 8051 controller that communicates over RS485 to other 8051 controller. The communication is half-duplex at baud of 57600, and...

Hi, I have an 8051 controller that communicates over RS485 to other 8051 controller. The communication is half-duplex at baud of 57600, and it works great. So far so good. Lately, I'm trying to make the 8051 device talk with a PC, since it is 57600 and I have RS232 RS485 converter this should be simple. I'm encountering strange problems at the 8051 reception, I never received what I se...